Telephone system



July l1, 1933. J. E. os'LlNE TELEPHONE SYSTEM Original Filed May '7. 1931 July l1, 1933. J. E. osTLlNE TELEPHONE SYSTEM 5 Sheets-Sheet 2 .mm2 S milk Original Filed May '7. 1931 Jal-1n E. CIE-.Hina

HTI-5.

July 11, 1933. J. E. osTLlNE TELEPHONE SYSTEM Original Filed May 7. 1931 5 Sheets-Sheet 3 July 11, 1933.

J. E. osTLlNE 1,917,390

TELEPHONE SYSTEM Original Filed May 7. 1931 5 Sheets-Sheet 4 7n use AL.

Jafm E. manne July 11, 1933- J. E. osTLlNE 1,917,390

TELEPHONE SYSTEM Original Filed May '7. 19251l 5 Sheets-Sheet 5 Ai. wir@ vw u] TONE Jul-m E. ll'l'line Patented July 11, 1933 JOHN E. OSTLINE, OF BERWYN, ILLINOIS,

ASSIGNR, BY MESNE ASSIGNMENTS, T0

ASSOIATED IELEZClLtIC` LABORATORIES, INC., 0F CHICAGO, ILLINGIS, A CORPORA- TION OF DELAWARE TELEPHONE SYSTEM Application led May 7, 1931, Serial No. 535,589. Renewed September' 9, 1932.

The present invention relates to telephone systems in general, but is concerned more particularly with telephone systems in which automatic switches are used to set up connec tions in response to numbers dialled by calling subscribers; and themain object, broadly stated, is the production of new and improved circuit arrangements in an automatic telephone system for simplifying the relay apparatus of the various individual switches so as to reduce the cost of the automatic equipment and to introduce such new operating characteristics as are found to be desirable or conducive to general economy in plant equipment.V

General'descm'ptz'on It is common practice in automatic telephone systems to provide each of the switches successively employed in a telephone connection with sufficient relay apparatus to enable it to receive impulses transmitted thereto from a calling line and perform its necessary functions. In order to make possible a more economical trunking network in multi-oiiice systems, and in order to render it unnecessary to adjust the control relays of the automatic switches to respond to the widely varying characteristics of the subscribers lines from which the controlling impulses are received, and for other purposes of a similar nature, automatic telephone systems have been developed employing register senders arranged to register the digits transmitted from the subscribers lines and to retransmit them to the automatic switches, making the necessary translation in the oilice-designating digits in accordance with-the most economical layout of interoiiice trunks and in accordance with the office originating the call.

The present invention is concerned with improvements in a system employing register senders for the purposes above outlined. Olie feature of the invention relates to the provision of cooperating circuit arrangements in the register senders and in the automatic switches, whereby operating impulses may be transmitted over one talking conductor directly from a register sender to the magnets of the automatic switches. It is a further feature that the other talking conductor is used to control a relay in each of the automatic switches which corresponds generally to the so-called slow-acting series rel-ay, one of which is ordinarily employed in each automatic switch to control the change-over operation at the end of a received digit.

An additional feature of the invention has to do with circuit arrangements in the automatic selectors, cooperating with circuit arrangements in the register senders so that a selector is caused to search over a group of trunk lines repeatedly when it finds all trunk lines in the group busy, this being accomphshed by causing a selector to be automatically restored to normal 'position when it nds all trunk lines in a groupI busy and by causing the register sender to repeat the previous digit so as to reoperate the selector to again bring it into association with the desired group of trunk lines.

A feature incidental to the preceding one has to do with an arrangement in the register sender for recording the number of times a digit is repeated to a selector and for stopping the repeating operation when a predetermined number of repetitions of the same digit have occurred. -In such a case, the operated switches are released and the calling subscriber is informed by a tone signal, hereinafter termed a veriiication tone, that he cannot obtain the number dialled.

According to a further feature, each connector is provided with a sequence switch which is arranged to be stepped over one of the talkingl conductors to transfer the operating circuit from the primary magnet to the secondary magnet and to shift the connector into testing position at the end of the secondary movement, all incidentalto the transmission to the connector of the tens and units digits. A special feature of this arrangement is that two additional control impulses are transmitted by the register sender to advance the sequence switch following its advance into the iirst testing position, advancing the sequence switch successively into its second and third test positions, whereby not only the busy or idle condition of the 100 nected thereto. In any case,

. mary line is determined, but a special test condi`` tion is obtained in case the terminals reached by the connector Wipers have no line conthe condition of the line as determined by the tests made is recorded in the register sender which, before becoming automatically disconnected, relays the condition of the called line to the primary unit located in the primary trunk of the connection, whereat arrangements are made for sending back any one of three tones to the calling line to inform the calling subscriber as to whether the line is busy, idle, or disconnected from the terminals, the tone indicative of the last condition being the hereinbefore-mentioned verication tone.

A feature of the arrangement above mentioned is that arrangements are provided in the primary unit for vautomatically releasing all of the operated numerical switches of a connection responsive to the test condition indicating that the called line is busy and' to the test condition indicating that the connectcor has been set on terminals not connected to a called line.

It is a further feature of the arrangement that talking current is supplied to both lines of an established connection from the primary unit of the primary trunk in use, except in interoice connections, wherein talking current is supplied to the called line from the incoming selector repeater in the called oce. A special feature of this arrangement is that the front and back bridges of the primary unit are disconnected under the control of the register sender when a connection has been set up in which talking current is not required or desired from the priunit, thereby extending the calling line metallicly and without bridges to the called line. This is advantageous, as for example when a connection is set up to a trunk line extended to the switchboard of a toll operator, as is well known.

An additional feature of the system disclosed herein is that when an interofiice connection is being set up the controls exercised by a register sender are repeated by an incoming seleetor repeater located in the distant oiice, andthat thisv selector repeater relays the necessary test and supervisory conditions back\to ward the calling end of the connection. The incoming selector repeater supplies talking current to the called line.

Additional objects and features of the invention relate to the` production of economical and commercial circuit arrangements for carrying out the objects and features hereinbefore enumerated and for giving the necessary supervision, a's will become more apparent as the description progresses.

Description of drawings Referring now to the accompanying drawings comprising Figs. 1 to 6, they show by ically to the selectors means of the usual circuit diagrams a suicient amount of apparatus in a telephone system embodying the features of the invention to enable the features to be understood. Figs. 1 to 3, which should be -placed end to end, show switching equipment which may be involved in a connection from the line of substation A, Fig. 1, to the line of substation B, Fig. 3; Fi s. 4 and 5, which should be placed in order low Fig. 1, show one of the register senders used to control the setting up of connections; and Fig. 6 shows the trunk circuit TC interposed between .an incoming trunk line and the jackJ located at the switchboard of an assistance operator.

Fig. 1 shows the oliice selector OS which is accessible to the lineswitch LS of the line of substation A by way of the trunk line comprising conductors 10S-108. The primary unit PU, including relays 109 to 117, is inserted in the trun line between conductors 106-108 and 124-126. The director selector DS is individual to the primary unit PU and has access to a group of directors or register senders, one of which is the director or register sender shown in Figs. 4 and 5. This director selector is of the same rotary type of mechanism as the ordinary rotary lineswitch, such as LS. The wipers 152-158 of the director selector DS are arranged to be driven in a forward direction only over a semi-circular bank of contacts and are arranged to be advanced upon the back stroke of the magnet 151. The ofce selector OS is a switch of the regular Strowger type, having wipers 17 9--181 which are arranged to be raised opposite the desired level of contacts bythe vertical magnet 178 and to be rotated over the contacts in the desired level by the rotary magnet 174. The release magnet 175 is provided for the purpose of restoring the selector to its normal position. The olf-normal contacts 170 and 177 close responsive to the shaft of the selector being raised from its normal position and are again opened when the selector is restored to its normal position. The overflow contacts 176 are arranged to be operated by a cam carried by the shaft whenever the wipers are driven over the last set of bank contacts in a level. The circuits of the lineswitch LS are well known and have not been illustrated.

Fig. 2 shows the thousands selector TH.S and the hundreds selector HS. The thouv sands selector THS is an incoming repeater terminating the incoming two-conductor trunk (185, 187), which is one trunk of the group accessible to the oliiceselector such as OS, Fig. 1. Mechanically, the switches THS and HS are each similar to the switch OS, Fig. 1.

The connector C, Fig. 3, is similar mechanexcept that it is provided with a sequence switch SE which has wipers 310 and 313 arranged to be operated 1 ICO one step upon each energization of operating magnet 311. The circuit-closing contacts 312 and 314 are arranged to be closed by a cam action at the same time the wipers 310 and 313 are driven onto the fifth associated contacts. The release magnet 308, which is the release magnet of the connector C, has an extension arm mounted on its armature and arranged to remove the holding dog (not shown) to bring about the .release of the sequence switch SE.

Referring now to Figs. 4 and 5, the director shown therein comprises the digit registers A-T, B-U, TH, and H, Fig. 5; the translator switch TS which is arranged to assume a position assigned to the called oiiice as indicated by the composite setting of wipers 512 and 517 of the registers A-T and B-U; and the counting switch CS which is arranged to count the impulses in the ofHce-code digits and numerical digits sent out under the control of the translator switch TS and the registers A-T to H, respectively.

The input control switch ICS, Fig. 4, is arranged to distribute the rst four series of incoming impulses to the registers A-T, B-U, TH, and H, respectively, and to distribute the fifth and sixth series of impulses to the registers A-T and B--U, which have become released in the meantime.

The output control switch OCS, Fig. 5, is arranged to render the register wipers successively effective to control the counting switch CS during the retransmission of irnpulses, and to control the transmission to the primary unit of the various switchthrough impulses, depending upon the test condition received from the switch train at the time the switch-through operation is performed.

' ciated magnet. Each wiper of one of these switches has a semi-circular bank of eleven contacts, as shown. The translating switch TS is of similar construction, having eight wipers, 1 to 8, which are arranged to be driven over a semi-circular bank of contacts by the operating magnet 535, being advanced upon the back stroke of this magnet. There are assumed to be twenty-five sets of contacts in the bank of the translator TS, although this number is purely arbitrary.

The repetition controller RC, Fig. '4, has

a wiper 429 which is arranged to be advanced one step over the associated contact bank each time the operating magnet 426 energizes, and

to be restored to normal each time release magnet 427 operates.

Throughout Figs. 4 and 5, there are a number of contact pairs associated with the various switches and labeled ON. In each case, these contacts are normally in the position shown in the drawings and are arrangedto close when the associated switch is moved from its normal position.r

Detailed description UaZZ from substation A to substation B When the subscriber at substation A removes his receiver he thereby closes a circuit over line conductors 101 and 102 for bringing about the operation of the lineswitch LS and the grounding of test conductor 103 so as to render the line busy in the banks of the connector switches having access to it. The wipers 103-105 of the lineswitch LS are advanced step by step in search of an idle trunk line. It will be assumed that the trunk line comprising conductors 106-108 is the first one found to be idle and that it is, therefore, seized. When this trunkline is seized, line relay 111 in the primary unit PU, which is normally bridged across the conductors 106 and 108 of the trunk line by way of contacts of relays 116, 109, and 110, operates over the calling line and closes a circuit for the slowrelease relay 112. Upon operating, relay 112 places ground potential on conductor 107 -at its upper armature by way of contacts of relays 109 and 110 thereby establishing a holding circuit for the lineswitch LS.

Seieing m idle director At its lower armature, line relay 111 connects test wiper 155 and operating magnet 151 together through the self-interrupting contacts of the operating magnet, thereby initiating the hunting movement of the director selector. The connection between wip-er 155 and magnet 151 includes armature 1.44 and its resting contact, armature 135, inner lower armature of relay 113, and armature 142, in addition to the lower armature of relay 111. The wipers 152-158 of the director selector DS are now driven step by step in search of an idle director, busy directors being marked by ground potential on the corresponding test contacts.

When release relay 112 operates as above mentioned, it places ground potential on locking conductor 147 at its inner upper armature, thereby closing a circuit by way of armatures 134, 149, and 141 for switching relay 116, which is arranged to operate and Vswitch the connection through to a director as soon as an idle one has been found by the director selector DS. The battery supply for relay 116 is obtained through the operating magnet 151 of the director selector Db through armature 142, inner lower armature of relay 113 and armature 135. As a result, relay 116 does not operate as long as Ithe free terminal of operating magnet 151 is maintained grounded by test wiper 155. As soon, however, as an idle director is reached, test wiper 155 encounters the ungrounded test contact of the idle director and the operation of magnet 151 ceases. At this point, relay 116 operates in series with magnet 151, but magnet 151 does not operate at this time because of the high resistance of relay 116.

When relay 116 operates, it connects Wipers 153 and 152 of the director selector DS4 to the incoming talking conductors 106 and 108 at its upper and lower armatures, at the same time disconnecting line relay 111 from conductors 106 and 108; at its inner upper armature and at armature 146 it connects Wipers 157 and 158 of DS to conductors 124 and 126 of the selector OS, at the same time disconnecting these conductors from the back-bridge battery-feed relay 117 at armature 145 it opens a point in a local circuit Jfor relays 113 and 114 and connects these relays to switch-through wiper 154; at its inner lower armature 1t connects relay 115 and the upper winding of relay 114 to the switch-through wiper 156; and at armature 144 it opens a point in the test circuit and connects test wiper 154 to the winding of release relay 112, thereby preparing a holding circuit for release relay 112, so that the relay will be held operated from the seized director after line relay 111 has fallen back.

In the seized director (assumed to be the director shown in Figs. 4 and 5), line relay 402, which is bridged across conductors 160, extending from the bank contacts on which Wipers 152 and 153 are now standing, energizes over the calling line by Way of conductors 106 and 108 and the upper and lower armatures of relay 116 of the primary unit PU. Upon operating, line relay 103 closes a circuit for release relay 403 which operates and prepares the director for operation. This preparation consists mainly in opening points in circuits of various restoring circuits and in preparing locking circuits for the relays. In addition, the impulse circuit over which the register sender is operated is prepared at the inner upper armature of relay 403, while at the upper armature of relay 403 ground potential is placed on conductor 162, thereby closing a. holding circuit by Way of wiper 155 and the operated armature 144 for release relay 112 of the primary unit PU. The ground potential on conductor 162, of course, serves also to mark the director selector engaged.

Dil tone With release relay 403 operated, current from the common dial-tone transformer 531, shown in the lower leftlhand corner of Fig. 5, is transmitted back to the calling line by way of the current-limiting condenser 522, contacts of rela 533, conductor 451, wiper 423 in first position, contacts of relay 404, armature 415, conductor 160, and thence to the calling line by way of the upper conductor thereof. The tone delivered by way of the above-traced circuit is of predetermined characteristics, and it indicates to the calling subscriber that he may nov:r operate his calling device in accordance with the digits in the desired number.

Dz'allng the number l5-1234 Upon hearing the above-described ldial tone, -the calling subscriber manipulates his dial in accordance with the digits in the desired number. When the first digit 4 is dialled, four interruptions are produced in the circuit of line relay 402 of the director, with the result that relay 402 deenergizes four times momentarily. The slow-acting release relay 403 does not fall back at this time as its circuit is only momentarily interrupted. Each time line relay 402 falls back, it closes a circuit for the operating magnet 507 of the register A-T, Fig. 5. This circuit includes the slow-acting series relay 404, distributing Wiper 425 and its first contact, and conductor 466. By the operation of magnet 507, the wipers 509-512 are advanced step-bystep until they come to rest on the fifth ofi'- normal set of bank contacts. Relay 404 responds to the first impulse of current delivered to its winding, and it remains operated throughout the series of impulses. At its inner armature, relay 404 opens the abovedescribed dial-tone connection, and at its lower armature it closes a circuit for operating magnet 421. Magnet 421 operates preparatory to advancing the wipers423-425, but the advance of these wipers does not take place until relay 404 falls back upon the termination of the series of impulses, at which time the Wipers 423-425 advance one step. Wiper 423 opens an additional point in the dial-tone circuit when it advances off the first contact; wiper 424 preparesa special start circuit by Way of conductor 495, which is not completed except when the first digitdialled is 0; and Wiper 425 shifts the operating conductor from the magnet of register A-T to the magnet of register B-U.

When the calling subscriber dials the second office digit 5, five impulses of current are delivered to magnet 513 of the register B-U, resulting in five operations of magnet 513 to advance the Wipers 515-517 five steps. Relay 404 responds again as above pointed out to advance the input-control switch ICS one step, advancing the operating circuit from the magnet of the register B-U to the magnet of the register TH.

In a similar way, the registers TH and H 'are operated to record the thousands digit 1 and the hundreds digit 2, the input-control switch ICS- being advanced one step at the A end of each digit, until its wipers now stand A upon the fifth set of bank contacts.

As will be explained hereinafter, the registers A-T and B-U have by this time controlled the setting of the translator switch TS. These registers have been released in position 4 of the switch ICS by relay 483, so that, having recorded and disposed of the A and B digits, they are now in normal position in readiness to record the tens and units digits. As' a result, the impulses in the tens digit are transmitted to the magnet of the register A-T by way of conductor 466, wiper 425 being at this time on its fifth bank contact. The sixth and last series of impulses is transmitted through the sixth contact in the bank of wiper 425 and over con- .ductor 467 to the register B-U.

Setting the translator switch As soon as the two office-designating digits 4 and 5 have beenrecorded on the first two registers A-T and B-U, respectively, the translator switch TS may be set in a position to correspond to the composite setting of these two registers, which operation is accomplished by starting the translator switch TS to operating in a buzzer-like manner to advance the wipers 1 to 8 over the sets of contacts successively and by stopping the operation of the translator switch when `the translation-stop relay 533 is able to operate in a circuit including wipers 1 and 2 in series, and controlled by wipers 512 and 517 of the first xtwo registers, respectively.

As soon as wiper 424 of the control switch ICS is advanced onto'its third bank contact at the end of the transmission of the second digit, conductor 460 is grounded, thereby completing a circuit through any one of the first nine off-normal contacts in the bank of wiper 10 and the said wiper for operating magnet 535 of the translator switch TS. This circuit includes contacts of relays 533 and 534. At the same time, a branch circuit is closed for interrupter relay 534 in series with resistance element536, but relay 534 does not operate for the time being because it is shunted by contacts of magnet 535. When magnet 535' operates, it removes the shunt from around the winding of relay 534, enabling relay 534 to operate and to open the circuit of magnet 535. Magnet 535 thereupon falls back and again shunts relay 534, whereupon relay 534 falls back and again connects up the operating magnet. This operation is repeated over and over, advancing the wipers 1 to 8 of the translator switch TS in a buzzer-like manner over the bank contacts. The two lower contacts in each set (the contacts wiped over by test wipers l and 2) are cross-connected on the intermediate distributing frame IDF tothe terminals of the conductors extending from the contacts in the banks of wipers 512 and 517. Bank contact set 538 is assigned to oliice 45. As a result, the Contactin this set engaged by wiper 2 is cross-connected by a jumper to the terminal connected with the fourth offnormal contact in the bank of wiper 512, and the lower terminal in set 538 is crossconnected to the terminal on the right-hand side of the distributing frame IDF to which the fifth contact in the bank of wiper 517 is connected. As a result, when the wipers 1 to 8 arrive upon the bank contact set.538 (45), a circuit is completed from ground by way of the grounded wiper 512 and the fourth associated off-normal contact, aj umper on the frame IDF, the next to the last contact in set 538, wipers 2 and 1, the bottom contact in set 538, the lower indicated jumper on the frame IDF, the fifth off-normal contact in the bank of wiper 517 and the said wiper, and the translation-stop relay 533 to battery. Upon operating, relay 533 locks ltself at its inner-lower armature to ground over conductor 452 and through armature 416 of release relay 403; it opens the o erating circuit of the translator switch T so as to stop the switch on contact set 538, at armature 552; it grounds wipers 505 and 506 at 451 from. the dial-tone transformer 531 and connects it to ground at its lower armature; and at its upper armature it grounds the rst six contacts in the bank of wiper 503 of the output-control switch OCS so as to supply ground potential through wiper 505 to start conductor 457 as long as the output control switch OCS is in any one of the first six posltions.

Sending out the office code The translating switch TSV has now been positioned on bank Contact set 538 under the control of wipers 512 and 517 of registers AT and B-U, respectively, and the 0fice code, as determined by the cross-connections on the I.D.F. from the contacts on which wipers 3 to 8 of the translator switch TS are now standing, may be sent out. It will-be noted that the contact in set 538, corresponding to office designation 45, on which wiper 3 of the translator switch TS is now standing is cross-connected by means of a jumper to the No. 2 digit-conductor and that the contacts now engaged by the remaining its upper armature; disconnects conductor wipers 4 to 8 in contact set 538 are cross-con- I use are cross-connected to the skip conductor in order to cause these positions to be skipped in the usual manner, and as will be pointed out subsequently. It will be understood, of course, that the six code-digit wipers 3 to 8 of the translator switch TS provide for a maximum of six code digits to'be redigits tervening oices to a called oiice located an 66 pares a locking circuit average distance away from the calling oice.

Returning now to the point at which start conductor 457 is grounded by the translation-stop relay 533 through wiper 503 oi the input-control switch, the placing of a ground potential on start conductor 457 closes a circuit through the motor-driven interrupter 413 for the lower` winding of the two-step synchronizing or pick-'up relay 412. As soon as interrupter. 413 closes, the lower winding of relay 412 is energized, whereupon the r'aly operates through its first step, closing its first-step inner-upper contacts, thereby closing a locking circuit for itself including both windings in series. No current Hows through the upper winding for the time being, however, because the same. potential is applied to both terminals.

As soon as interrupter 413 opens, the shunt is removed from around thelupper winding of relay 412, whereupon the relay operates fully. At its upper armature, relay 412 transfers the interrupter from the junction of its own windings by way of the middleupper armature and resting contacts of .relay 409 and conductor 474 to the operating magnets 541 of theA counting switch CS, and at its lower armature it closes a circuit for the digit-start relay 411, whereupon relay -411 operates and closes a circuit at its lower armature and over conductor 454 for ma et 501 of the outputi-control switch OCS. agnet 501 thereupon operates preparatory to advancing wipers 503-506 in a counterclockwise direction upon its deenergization. At its middle-lower armature relay 411 prepares a circuit for relay 409, which is not closed until all of the digits have been sent out, and at its inner-upper armature it preor stop relay 410. At its upper armature, relay 411 removes the shunt from around interrupter 414 (both interrupters are now in their open position) and closes a circuit for reversing relay 408.

65k-Relay 408 thereupon operates and shifts the shift conductor 164I` an extension of the loW- transmitted in order to trunk thev call to the er outgoing talking conductor 126, Fi 1, from its previous connection to ground by way of test relay 407 to battery through the associated resistance element; and at its middle-upper armature it .shifts conductor 165, an extension of the upper outgoing talking conductor 124, Fig. 1, from its previous connection to battery through the associated'resistance element to the free terminal of the interrupter 414. It will be understood, of course, that the operation of relay 412 through its second step, the operation of the digit start relay 411, and the above-described operation of reversing relay 408, all take place responsive to interrupter 413 arriving at open position and before interrupters 413 and 414 arrive in their next closed position. The application of battery potential to conductor 164 in place of the ground potential formerly connected thereto is or the purpose of'enabling the control relay of the automatic switch to be controlled properly as will be pointed out hereinafter, and the shifting of conductor 165 from its previous battery connection to ground by way of the interrupter 414 is to enable the impulses to be delivered to the operating magnet of the switch to be operated.

Following the above-described operation of relays 412, 411, and 408, each subsequent closure of the interrupters 413 and 414 results-in an impulse being delivered by interrupter 414 over conductor '165 to the operating magnet of the connected switch, and in an impulse being delivered by interrupter 413 over conductor 475 to the operating magnet 541 of the counting switch CS. The efect of the impulses being delivered to the switch train will be considered later. Each time an impulse is delivered to magnet 541 of the counting switch CS, this magnet energizes preparatory to advancing the wipers upon the termination of the impulse. Accordingly, wipers 543 and 544 are advanced one step at the end of each impulse delivered to the switch train and to the counting switch.

When stop Wiper 544 is advanced into engagement with its second off-normal contact at the end of the second impulse delivered to magnet 541, it encounters the No. 2 digit conductor on which a ground potential has been placed by way of the contact in group 538 encountered by wiper 3 of the translating switch TS and a jumper on the intermediate distributing frame IDF, wiper 3 being grounded by way of wiper 505 of the output-control switch OCS in position 1. As

a result of this, a circuit is closed over the No. 2 digit conductor and through stop wiper 544 of the counting switch for the stop relay 410, Fig. 4. When relay 410 operates, it closes a locking circuit for itself at its inner-lower armature through contacts of the operated relay 411, and at its middle-upy llC per armature it opens the circuit of reversing relay 408. Reversing relay 408 thereupon falls back and again connects the conductors 164 and 105 to ground through relay 407 and battery through the associated rcsistance, respectively. The lower terminal of relay 407 is now grounded independent of intcrrupter 414 through the inner-upper contacts et' relay 408 and the upper contacts of the operated -rclay 410. It will be understood, of course, that the energization of relay 410 and the deenergization of relay 408 occur while the interrupters 413 and 414 are in their open position following the l" transmission of the last impulse in the first digit by interrupter 414. The transmission of further impulses by interrupter 414 is prevented now by the shunt around this interlrupter through the contacts of relays 408 20 and 410.

As a further result of the energization of relay 410, the start conductor 457 is opened at armature 433, whereupon pick-up relay 412 falls back. At its inner-upper armature, re- 5 lay 410 connects conductors 477 and 474 together by way ot' contacts of relay 409, thereby closing a self-restoring circuit for'the counting switch magnet 541 through wiper 543. Magnet 541 now operates in a buzzer- 3D"like manner in its self-interrupting circuit over conductors 476 and 474 until it arrives in the normal position shown in the drawings, at which time the operating circuit is opened y -when wiper 543 passes ofi` the last-grounded bank contact.

When Wiper 543 passes off the last-grounded bank contact and opens the self-restoring circuit, the circuit of slow-acting digit-start relay 411 is opened, resulting in the deenergization of this relay after the interval for which it is adjusted. ,Vhen relay 411 falls back, it opens an additional point in the circuit of reversing relay 408 at its upper armature, at the same time placing an additional shunt around interrupter 414; opens the locking circuit of the slow-acting stop relay 410 at its inner-lower armature; and at its lower armature it removes ground potential from conductor 454, thereby opening the circuit of the operating magnet501 of the outgoing-control switch OCS. It may be pointed out at this time that ground potential is not removed from conductor 454 at this time in case test relay 407 is held operated over the trunk line extending to any switch in the train, in the event that an operated selector has not yet found an idle trunk, in which case magnet 501 of the output-control switch OCS remains operated until test relay 507 is deenergized over the trunk line, as will be pointed out hereinafter.

When magnet 501 falls back and advances the wipers 503-506 one step, wiper 505 disr connects ground potential from wiper 3 of the translator switch TSI and connects ground potential to wiper 4. Since the fourth to eighthcontacts in contact set 538 '(on which the wipers 1 to 8 are now standing) are cross-connected by jumpers to skip conductor 464, a self-interrupting circuit is 7 potential is supplied to start conductor 457 by wiper 503 through wiper 523 of the hundreds register H and any associated offnormal contact.

Retransmz'ttz'ng the numerical dgts When the stop relay 410 falls backafter the interval for which it is adjusted and following the restoration of relay 411, it again extends the grounded start conductor 457 to the two-step pick-up relay 412, with the result that pick-up relay 412 is operated through its first step by interrupter 413 and operates through its second step in the hereinbefore described manner when interrupter 413 again opens. Following the operation of relay 412, the transmission of the thousands digit l is started, with relays 411 and 408 operated as hereinbefore pointed out.

When the wipers of the counting switch are advanced one step at the end of the first impulse transmitted to the switch train, wiper 544 arrives on the contact connected with the first digit conductor, now grounded through wiper 520 of the thousands register TH, on which the digit l has been registered. Stop relay 410 operates to terminate the digit in the manner hereinbefore described.

Incidental to the deenergization of relay 411, when the counting switch CS has been restored to its normal position responsive to the operation of relay 410, magnet 501 of the output-control switch OCS, which was operated over conductor 454 upon the energization of relay 411, falls back and advances the wipers of the output-control switch an additional step preparatory to retransmitting the hundreds digit.

Following the retransmission of the hundreds digit 2,stored on the hundreds register H, the output-control switch OCS is advanced to position 9, in which position ground potential is extended to wiper 511 preparatory to retransmitting the tens digit 3, stored on register A-T, and the output-control switch OCS is advanced to position 10 at the end of the transmission of the tens digit, preparatory to the retransmission of the units digit 4, stored on register B-U. With wiper 505 in position`10, ground potential is extended to relay 539, which o erates and extends ground potential to digit wiper 515 preparatory to operating the stop relay 410 at the. end of the units digit. Wiper 516 is maintained normally disconnected from conductor 47 0 so as to avoid a premature grounding of this conductor by way of whichever digit conductor wiper 516 happens to be standing on. With conductor 470 grounded responsive to wiper 505 arriving at position 10, a circuit is prepared for the test-start relay 409, which is closed through the middle-lower armature of the digit start relay 411 and through armature 431 as soon las stop relay 410 operates at the end of the units digit. Upon operating, relay 409 at its inner lower armature locks itself operated through the inner-lower contacts of the operated release trelay 403; opens a point in the circuit of the repetition-control relay 406 at its middle-lower armature; opens the branch holding circuit for the magnet of the output-control switch OCS at its lower armature; opens an additional point in the circuit of reversing relay 708 at its upper armature; and at its inner-upper armature it transfers the impulse circuit from the operating magnet of the counting switch CS to stop relay 410. As a result, when pick-up relay 412 is again operated, no impulses are delivered to the operating magnet of the counting switch CS; but, instead a single interruption is produced in the circuit established through test relay 407 and over conductor 164, as will be hereinafter explained, following which stop relay 410 is operated to introduce a pause before the next open impulse is transmitted. The impulses transmitted following the operation of the test-start relay are impulses for the purpose of driving the sequence switch of the connector in use (the sequence switch SE,

Fig. 3, for example) through its third and fourth positions, as will be explained hereinafter.

Trwnkz'ng the call to the desired oyice Returning now to the point at which the director operates to send out the single oiicecode digit 2, it will be recalled that the two closed impulses constituting this digit are sent out by interrupter 414 over conductor 165, while the reversing relay 408 is operated, and while conductor 164 is connected tov battery by way of the operated upper armature of relay 408 and the associated resistance element. Responsive to these two impulses, which are transmitted by way of conductor 165, wiper 158, inner-upper armature of the operated relay 116, and conductor 124, vertical magnet 178 operates to raise the wipers 17 9-181 stepby-step until they come to restnet 174 and for release magnet 175, while oH- normal contacts 17 O prepare a circuit for the. lower windin of the two-step change-over relay 171. Re ay 171 does not operate for the time being because thereis no ground potential applied to conductor 126 at this time; rotary ma et 174 does not operate at this time because its circuit is open at the middle-upper armature of relay 171, and the release magnet 175 does not operate at this time because its circuit is held open at the upper armature of relay 171, which first-step upper armature of the relay is operated res onsive to current flowing through the relatively ineiiicient upper winding of the relay over the grounded incoming release-trunk conductor 125.

When reversing relay 408 of the director falls back responsive to the energization of stop relay 410 at the end of the transmission of the code digit 2, it shifts conductor 165 from the impulse circuitto battery by way of the associated resistance element and it shifts conductor 164 to ground through test relay 407, the circuit to ground being completed momentarily through the inner-upper contacts of relay 408 and the upper contacts of relay 410, and subsequently to the upper contacts of relay 411. The application of battery potential to conductor 165 has no particular effect at this time, but the application of ground potential to conductor 169 through relay 407 results in the operation of relay 407 and in the operation of change-over relay 171 of the oiiice selector OS through its second step, as the lower winding of this relay is connected in series with test relay 407 by way of off-normal contacts 17 0. Relay 407 in the director prepares certain circuits, and momentarily closes a holding circuit for the operating magnet of the output-control switch OCS, but this has no effect upon the normal operation of the system, as will be extinues until an idle trunk line (characterized by the presence of a battery potential on the test contact thereof) is found. When an idle trunk line is reached, which trunk line it will be assumed is the one comprising conductors and 187 and extending to the called exchange whereat it terminates in the incoming selector repeater or thousands selector THS, Fig. 2, the upper winding of switching relay 172 is energized in series with resistance element 186 by way of test wiper 180. Relay 172 thereupon operates ,and closes *a locking circuit for itself to the incoming release trunk conductor 125 at its inner-lower armature; opens the circuit of rotary mag-- net 174 and an additional point in the circuit of release magnet 175 at its inner-upper armature, thereby stopping the rotary movement and preventing a premature operation of the release magnet; disconnects the incoming release trunk conductor 125 from the upper winding of relay 171 at its middle-lower armature and extends it to wiper 180, thereby applying a ground potential to the multiple test contacts of the seized trunk to mark the trunk line engaged; and at its upper and lower armatures it disconnects the incoming talking conductors 124 and 126 from vertical magnet 178 and the lower winding of changeover relay 171 and extends them by way of wipers 170-181 to the trunk line conductors 185 and 187. When this occurs, relay 171 falls back, as does test relay 407 in the director. It will be understood, of course, that this hunting operation is completed before the slow-acting relays 411 and 410 have hadtime to fall back one after the other in the course of their inter-digit timing operation.

In the incoming selector THS, Fig. 2, the oppositely polarized relays 201 and 202 are included in a bridge across conductors 185 and 187 in series with the high resistance element 207. Current, therefore, iows in a loop circuit over conductors 185 and 187 and through these relays, as well as through the test relay 407 of Fig. 4. Relay 407, being mar-v ginally adjusted, does not operate at this time because of the current-limiting eiiect of resistance element 207; impulse relay 202 does not operate at this time because of the direction in which it is polarized; but relay 201 operates and closes a circuit through contacts of change-over relay 205 for release relay 204. lVhen thus operated by holding relay 201, relay 204 prepares a circuit for switching relay 206 at its upper armature; prepares a circuit for change-over relay 205 at its inner-lower armature; and it opens a point in the circuit of release magnet 214 at its lower armature.

Operating 2571.0 incoming thousands selectorrepeater THY Following the sending out of the single code digit 2, which effects the trunking of the connection to the desired oiiice by Way of the trunk line extending to the thousands selector THS, the director retransmits the stored thousands digit 1, as hereinbefore pointed out. It will be recalled that reversing relay 408 in the director is operated just prior to the sending out of any digit, being operated at the upper contacts of relay 411 during the open period of interrupters 413 and 414 re- `reversing relay 408 in pick-up relay 412 operates fully upon its upper winding being brought into play by in- 'terrupter 413 coming into open posltion.

It will be recalled also that reversing relay 408 shifts the connection of conductor 164 from ground to battery and shifts the connection of conductor 165 from battery to the now-open, ground-impulsing interrupter 414. When this occurs, the current-flow in the bridge across conductors 185 and 187 at the thousands selector TI-LS, Fig. 2,`ceases, and relay 201, therefore, falls back. Upon falling back, relay 201 opens the circuit of the slow-acting release relay 204 and closes a circuit for change-over relay 205 by way of the inner-lower armatures of relay 204 and 203, and the resistance element 215. Relay 205, however, does not operate at this instant because it is short circuited by ground potential applied to its lower terminal through the back contacts of relay 202 and 4its own middle-lower armature.

- Following the above-mentioned operation of reversing relay 408 of the director, interrupter 414 operates to retransmit the impulses (in this case a single impulse corresponding to the digit 1) in the thousands digit. Each time the interrupter 414 closes, current flows oyer the established loop to the thousands selector' THS and including conductors 185 and 187. Impulse relay 202 responds to each closure of the interrupter 414. Each time it responds, impulse relay 202 closes a circuit for vertical magnet 212 by way of the upper armatures of relays 205 and 206, relay 205 responding at the beginning of the first operation of relay 202 when the shunt is removed from around its winding at the back contact of the armature of relay 202. Vertical magnet 212 responds by raising thel wipers 216-218 stepby-step until they come to rest opposite the desired level of bank contacts (in this case the first level). In addition to completing the vertical-magnet circuit at its upper contacts, change-over relay 205 shifts the circuit of release relay 204 so that the release relay is in multiple with the vertical magnet during impulsing and is thereby prevented from falling back, as it receives an impulse each time the vertical magnet does. relay 205 also opens a point in the path over which it was shunted by back contacts of relay202 just prior to its operation, so that l it is not shunted by relay 202 lng.

At the end of the digit being transmitted, the director falls back responsive to the opening of its circuit at the middle-upper armature of stop relay 410. When this occurs, current-flow in the normal direction is resumed over the talking conductors extending to the switch train, and holding relay 201 reoperates. When it during impuls- Change-over docs so, relay 201 opens the circuit of changeover relay 205, whereupon change-over relay 205 falls back and again shifts release relay 204 into connection with the front contact of the armature vof relay 201, reestablishing the normal holding circuit of relay 204. The lower winding of battery-feed relay 203 is now energized through the front contacts of relay 201, the lower right-hand repeating-coil windin lower contacts of relays 205 and 206, o -normal contacts 209, and resistance 215. Rela 203, therefore, operates and closes the sel -interrupting rotary-magnet circuit for rotary magnet 213 at its lower armature, which circuit includes ott-normal contacts 210, inner-lowerarmature of switching relay 206, and contacts of release magnet 214. Magnet 213 accordingly operates in a buzzer-like manner to advance the wipers 216-218 across the bank contacts in the selected level in search of an idle trunk line. Relay 203 also shunts the high-resistance element 207 at its upper armature, increasing the current flow over the loop including conductors 185 and 187 sufficiently to operate the marginal test relay 407 in the director.

When an idle trunk line is reached, which trunk line it will be assumed is the one comprising conductors 219- 221 and extending to the hundreds selector HS, the upper winding of switching relay 206 is energized through test wiper 217 and over conductor 220, in series with resistance element 273, which is shunted around the upper winding of the two-step change-over relay 271 in order to provide a fast-energizing circuit for relay 206. lVhen relay 206-operates, it opens the rotary-magnet circuit and closes a locking circuit for its lower winding at its inner-lower armature; shunts its own upper winding at its inner-upper armature so 'as to apply a guarding ground potential directly to the test contact; and at its upper and lower armatures disconnects vertical magnet,

212 and the lower winding of battery-feed relay 203, respectively, and connects up wipers 216 and 218. When this Occurs, battery-feed relay 203 falls back and again inserts the high resistance element 207 in the bridge across incoming conductors 185 and 187, whereupon marginal test relay 407 in the director falls back. The two-step change-over relay 271 in the hundreds selector HS pulls up through its first step and opens a point in the circuit of release magnet 275 responsive to the upper winding of relay 206 being shunted at the innerupper cont-acts of the relay, as above pointed out.

When the sending loop is opened in the director as hereinbefore described just prior to the transmission of the first impulse in the hundreds digit, relay 201 falls back and again closes a circuit for the shunted changeu over relay 205 through resistance element 215, with the result that relay 205 operates responsive to the shunt being opened at the back contacts of relay 202 at the beginning of the first impulsein the hundreds digit. With relay 205 operated, and with relay 206 operated, each impulse in the hundreds digit is transmitted through wiper 216 and by way of trunk conductor 219 to the vertical magnet 278 of the hundreds selector HS. By this operation of the hundreds selector HS, the w1 ers 279-281 are raised step-by-step until t ey come to rest opposite the second level of bank contacts (the hundreds di it being a 2). Off-normal contacts 270 and 2 7 close as soon as the selector is raised from its normal position, and off-normal contacts 270 connect the lower winding of relay 217 to the lower talking conductor 221.

lVhen, at the end of the'hundreds digit 2, the current-How over conductors 185 and 187 is resumed in the normal direction and relay 201 pulls up, change-over relay 205 falls back responsive to its circuit being opened at the contacts of relay 201 and it again connects the lower winding of battery-feed relay 203 to conductor 221 by way of wiper 218. When this occurs, relays 203 and 271 energize in series over conductor 221, and relay 203 shunts the high-resistance element 207, permitting the marginal-test relay 207 in the director to operate.

In the hundreds selector HS, when relay 271 operates in series with the lower winding of relay 203, it closes a locking circuit for itself at its lower armature independent of off-normal contacts 270; prepares a test circuit for the upper winding of relay 272 at its inner-upper armature; and at its middleupper armature completes the self-interrupting circuit for rotary magnet 274. Rotary magnet 274 thereupon operates in a buzzer-like manner to advance the wipers 279-281 step-by-step over the contacts in the selected level. When an idle trunk line is reached, which trunk line it will be assumed is the one comprising conductors 285-287 and extending to the connector C, Fig. 3, the upper winding of relay 272 is energized through test wiper 280 and over release-trunk conductor 286, in series with the lower winding of release relay 301. Relay 27 2 thereupon operates and closes a locking circuit for its lower winding at its innerlower armature; disconnects the incoming release-trunk conductor 220 from the upper winding of relay 271 and extends it by way of contacts of release magnet 275 to test wiper 280; and at its upper and lower armatures disconnects the incoming talking conductors 219 and 221 from vertical magnet 278 and the lower winding of relay 271 and connects them by way of wipers 279 and 281 to conductors 285 and 287 extending to the connector C. When this occurs, relay 271 of the hundreds selector HS and relay 203 of the thousands selector THS, whose lower windings have been maintained energized in series over conductor 221, fall back. When relay 203 falls back, it re-inserts the high resistance element 207 in the bridge across conductors 185 and 187, whereupon the marginal test relay 407 in the director falls back to indicate that an idle trunk line has been found.

In the connector C, it will be noted that the right-hand terminal of the vertical magnet 204 is normally connected to battery by sequence-switch wiper-arm 310 in position 1, and that the other terminal of vertical magnet 204 is normally connected to incoming conductor 285. As a result, when the three impuses constituting the tens digit 3 are delivered from the impulse relay 202 of the thousands selector THS by way of conductors 219 and 285 and through wipers 216 and 279 to vertical magnet 204 of the connector C, vertical magnet 204 responds tol each of the three impulses and raises the wipers 315-317 step-by-step until they arrive opposite the third level of bank contacts. Ott-normal contacts 309 and 307 close as soon as the wipers of the connector are raised from their normal position, and off-normal contacts 307 close a point in the circuit of release magnet 308, but release magnet 308 does not operate at this time as its circuit is maintained open at the inner-lower contacts of release relay 301. Off-normal contacts 306 are opened as soon as the wipers are raised from normal position, and they open the connection between the lower winding of relay 301 and the incoming grounded release trunk conductor 286. Release relay 301, however', remains operated through its inner-upper contacts and through both of its windings in series.

lVhen the lower winding of the batteryfeed relay 203 is again connected up in the thousands selector 'TI-LS at the lower contacts of relay 205` upon relay 205 falling back at the end of the digit, current iiows through the lower winding of battery-feed relay 203 and over the lower conductor of the established connection to the connector C and thence to battery by way of off-normal contacts 309, operating magnet 311 of the sequence switch SE, and the associated highresistance element to battery. The marginally-adj listed battery-feed relay does not operate at this time because of the currentlimiting effect of the high-resistance element 318, but the operating magnet 311 of the sequence switch SE operates and advances the wipers 310 and 313 from position 1 to position 2, wiper 310 shifting battery potential from the vertical magnet to the rotary magnet.

Vhen the four impulses of the units digit are transmitted to the connector over con- The operating magnet 311 of the sequence switch SE is deenergized at the beginning of the transmission of the units digit when holding relay 201 in the thousands selector THS falls back and opens its circuit. Therefore, when magnet 311 energizes again responsive to the operation of holding relay 201 at the end of the units digit, it advances the wiper arms 310 and 313 of the sequence switch SE from position 2 to position 3, the busy-test position. At this point a test is made to determine whether or not the called line is busy, and a subsequent test is made to determine whether or not the called line is disconnected from its terminals, in case it does not test busy, following which the connection to the line is completed and ringing current is applied if the second test made indicates that the line is connected to its terminals in the connector bank.

The called Zine tests busy When the wipers 310 and 313 of the sequence switch SE are advanced into third position in the manner above described, wiper 310 prepares to shunt the high-resistance element 318 by way of contacts of test relay 302. At the same time,'wiper 313 of the sequence switch SE connects the upper winding of test relay 302 to the test conductor 323 of the called line by way of wiper 316. Therefore, if there is a ground potential on conductor 323 (applied either through another connector having access to the line or through the line-switch individual to the line) because the line ot substation B is engaged, an operating circuit exists for the battery-connected upper winding of relay 302, and relay 302 operates, thereby placing a shunt around the high-resistance element 318 so as to permit sufficient current to flow through magnet 311 and over the lowertalking conductor to operate the marginally-adjusted battery-feed relay 203 of the thousands selector THS. lVhen batteryfeed relay 203 operates at this time, it shunts the high-resistance'element 207 in the bridge across the incoming talking conductors 185 and 187, permitting the test relay 407 in the director to operate. This operation of relay 407 occurs at the same `time that the out put-control switch OCS, Fig. 5, is driven into eleventh position, following the retransmission of the units digit. With the outputcontrol switch in osition 11, and with test relay 407 energize a characteristic switchthrough circuit is completed over conductor 161 to the primary unit PU as soon as stop relay 410 falls back following the deenergization of relay 411. This circuit extends from ground by way of the grounded wiper 505 of the output-control switch OCS in position 11, resistance element 525, conductor 465, lower contacts of relays 410 and 407, conductor 161, wiper 154 of the director selector DS, armature 145, and the lower windings of relays 114 and 113, to battery. The marginally-adjusted relay 114 does not operate at this time on account of the current-limiting eect of resistance 525. Re-

lay 113, however, operates and closes a lock-A ing circuit for its upper winding to locking conductor 147, grounded at the inner-upper contacts of release relay 112; removes ground potential from release trunk conductor 125 extending to the @Hice selector OS at its armature 148; disconnects battery-feed relay 117 from the intermediate section of the 'talking conductors at its upper armature and at armature 138, so as to prevent relay 117 from becoming connected up; opens an additional point in the test circuit of the director selector DS at its inner-lower armature; completes the busy-tone circuit at armature 139; and at armature 149 opens the circuit of the director-selector switching relay 116. Relay 116 now falls back and disconnects wipers 152-158 of the director selector DS, thereby freeing the director and permitting it to restore to normal position in a manner to be explained hereinafter. Relay 116 also again connects up line relay 111 to the incoming talking conductors 106 and 108, permitting line relay 111 to operate over the calling line and close a holding circuit for release relay 112. Busy-tone current is now supplied to the calling line over the common busytone conductor 167 and through armatures 143 and 139 to the lower talking conductor, by way of the resting contact and armature 137, and talking condenser 119.

Upon hearing the busy tone thus supplied to his line, the subscriber at substation A is expected to replace his receiver to permit the relays in the primary unit PU to restore responsive to the deenergization'of relays 111 and 112.

The connection established by way of the switches OS, TH.S, and HS to the connector C is released responsive to the falling back of relay 116, and to the operation of armature 148 of relay 113, as conductors V124-126 are now completely disconnected.

The way in which the release of the operated switches is accomplished will be eX- plained hereinafter.

The called lime disconnected i It will now be assumed that the called line has been disconnected from the connectorbank terminals, as for example when a new number has been assigned to the `called line.

switch SE. Accordingly, the director is not disconnected for the time being and an additional impulse is transmitted by the director to advance the sequence switch SE from position 3 to position 4, as will now be pointed out.

It has been pointed out hereinbefore that test-start relay 409 is operated throu h contacts of relays 410 and 411 when re ay 410 energizes at the end of the units digit and while the output-control switch OCS, Fig. 5, is in position 10, and that relay 411 Jfalls back after a slight interval to permit the advance of the output-control switch OCS from position 10 to position 11 to permit the hereinbefore-described busy test to be performed. Now, when this test does not indicate a busy condition of the called line, as evidenced by the failure of test relay 407 to operate while the output-control switch OCS is in position 11, the two-step pick-up relay 412 is again operated through the interrupter 413 following the deenergization of stop relay 410. Pick-up relay 412 operates through its second step just as interrupters 413 and 414 arrive in open position. Relay 411 operates responsive to the closure of the lower contacts of relay 412 at this time and removes the shunt from around the now-open interrupter 414 in the usual manner. Relay 411, however, does not bring about the operation of reversin relay 408, as relay 409 has been operated. emoving the shunt from around the interrupter 414 while it is in open position opens the circuit which has been previously established through test relay 407 and over the two talking conductors in series for holding relay 201 in the thousands selector THS, Fig. 2. Relay 201 falls back at this time and opens the circuit previously established over the lower talking conductor for the operating magnet 311 of the sequence switch SE in the connector C. Magnet 311 thereupon falls back preparatory to again advancing the wipers 310 and 313.

In the director, interrupters 413 and 414 close again after a very slight interval, and interrupter 414 again closes the loopcircuit through holding relay 201 of the thousands selector TH.S. Relay 201 reoperates and closes the operating circuit over the lower outgoing talking conductor for the operating magnet 311 of the sequence switch SE. Magnet 311 thereupon operates and advances the wipers 310 and 313 into fourth position.-

Wiper 310 places a shunt around the highresistance element 318 so as to relay back to a disconnected-line indication to the director, but wiper 313 connects test wiper 316 of the connector to the grounded lower Winding of test relay 302 so as to operate test relay 302 in series with the usual cut-off relay associated with the called lineswitch in case the line. is not disconnected, and thereby remove the shunt from around resistance 318. In the present case, however, the line is assumed to be disconnected, and test relay 302 does not operate. i

With test relay 302 non-operated in position 4 of the sequence switch SE, the shunt placed around the resistance element 318 permits` suicient current to flow over the lower talking conductor to operate the marginallyadjusted battery-feed relay 203 of the thousands selector TH.S to shunt the resistance element 207 and permit the marginally-adj listed test relay 40T of the director to operate.

In the director, while the above-explained operations have been taking place responsive to interrupter 414 arriving in closed position, the. stop relay 410 has operated responsive to interrupter 413 arriving in closed position, a nd in a circuit including the upper armature ol the operated relay 412 and the inner-upper armature of the operated relay 409, and has opened the switch-through circuit at its lower armature so as to prevent it from being completed at the lower armature of relay 40T until the output-control switch OCS has heen advanced into position 12.

When stop relay 410 operates, it locks itself at its inner-lower armature to ground by way of the contacts of relay 411 in the usual manner, and it opens the circuit of pick-up relay 412 at armature 433. Pick-up relay 412 falls back and opens the circuit of rela 411, with the result that relay 411 falls bac after a slight interval and removes ground potential from conductor 454, permitting inagnet 501 of the output-control switch-..to

fall back and advance the wipers 503-506 into position 12. v

lith the output-control switch in position 12, ground potential is supplied by wipers 506 directly to conductor 465, independent of the current-limiting resistance 525. Accordingly, when stop relay 410 falls back after a slight interval, responsive to the opening of its locking circuit at the inner-lower armature of relay 411, it completes a circuit from the now-grounded conductor 465 at its lowercontacts and through the lower contacts of the now-operated test relay 407 and over conductor 161 for the lower windings of relays 113 and 114 in se.- ries. Relays 113 and 114 both operate at this time and bring about` the release of the operated switches and the disconnection of the director in the hereinbeore-described manner. In addition, the marginally-adjusted calling subscriber is expected to replace his a receiver and free the primar units PU and allow it to clear out, and to ook in the telephone directory to ascertain that he called the listed number. If he has called the listed number, the calling subscriber is expected to remove his receiver and call the verification operator, to whose position the connection will be completed in a manner to be pointed out hereinafter.

The called Zine z'dle It will now be assumed that the line of substation B is idle when called and that it is not disconnected from the terminals, in which case the advance of sequence switch SE through position 3 and into position 4 takes place as hereinbefore described. With the sequence switch SE in position 4, and with the line of substation A idle, a circuit is closed through the lower winding of test relay 302 by way of wipers 313 and 316 and in series with the cut-olf relay of the lineswitch connected to the calledline. With test relay '302 operated, resistance element 318 is not shunted by sequence switch wiper 310 in position 4, and'the disconnected-line indication is not transmitted back to the director. i

In the director, the hereinbefore-dcscribed switch-through circuit is not closed over conductor 161 in position 12 ofthe output-control switch OCS, because the test relay 407 is not in an energized osition when stop relay 410 falls back. Undxr this condition, the deenergization of stop relay 410 is followed by the connecting up and by the operation of the 'two-step pick-up relay 412, responsive to which the digit-start relay 411 is again operated to perm1t interrupter 414 to produce an additional momentary interruption -in the outgoing control loop. Responsive to this interruption, which is repeated at holding relay 201 of the thousands selector TI-LS, Fig. 2, operating magnet 311 of the sequence switch SE in the connector C momentarily falls back and then reoperates to advance the wipers 310 and 313 into position 5 to complete the connection to the called line. With wiper 313 in position 5, ground potential is applied directly to wiper 315 to mark the called line engaged. Contact springs 312 and 314' are operated by the well-known cam ar- Y ground to the lower conductor of the called line through the lower armature of release relay 301 and wiper 317. Ringing current is now intermittently applied to the called line to signal the called subscriber in the usual manner.

Ulearz'ng out the director In the director, stop. relay 410 is again operated by interrupter 413, when (interrupters 413 and 414 close following the abovementioned interruption in the outgoing-control circuit with the output-control switch in position 12. Following the operation of stop relay 410, relays 412 and 411 release, and

relay 411 opens the circuit of magnet 501 of the output-control switch OCS, permitting .this magnet to fall back and advance the wipers of the output-control switch into position 13. With the output-control switch in position 13, a circuit is closed from the grounded wiper 506, through the resistance element 526, and over conductor 163, wiper 156, inner-upperfarmature of relay 116, relay 115, and the upper winding of relay 114, to battery. Since the upper winding of relay 114 has a relatively large number of turns, relay 114 energizes over the above-traced circuit notwithstanding the inclusion of the resistance element 526, Fig. 5, in its circuit, but the marginally-adjusted relay- 115, which has a relatively small number of turns, is unable to loperate because of the current-limiting eiect of resistance element 526. When relay 114 operates, it closes a locking circuit for its upper winding at its inner-upper armature and through contacts of the operated release relay 112; connects up the ringing-tone cony ductor 166 at its lower armature so as to send back a characteristic ringing tone to the calling line to inform the calling subscriber that ringing current is being applied to the called line; prepares a circuit for the answering supervisory relay 110 at armature 140; prepares to send back an impulse of current from the booster battery 122 at its upper armature opens an additional point in the test circuit of the director selector DS at armature 142; and at armature 141 opens the circuit of the director-selector switching relay 116, whereupon relay 116 falls back and disconnects the wipers 152-158 of the director selector DS.

In the director, when the wipers 152-158 of the director selector are cut olf, line relay 402V falls back and opens the circuit of the 'slow-acting release relay 403. Series relay 404 does not operate at this time because wiper 425 is standing on a disconnected contact. After a slight interval, release relay 403 falls back and opens the locking circuit of the test-start relay 409 at its inner-lower armature, opens an additional point'in the previously-established dial-tone circuit at armature`415; opens the locking circuit of translation-stop relay 533 at armature-416; and at armatures 434-440 it closes restoring circuits over conductors 441-447 for the output-control switch OCS, the registers A-T, B-U, TII, and H, the counting switch CS, and the'input-control switch ICS, respectively. As a result, the above-named mechanisms are operated in a step-by-step manner by thel buzzer-like action of thelr respective stepping magnets until they arrive in normal position. These restoring circuits are opened at off-norma1 contacts 502, 508, 514, 519, 522, 542, and 422, respectively. Normally, the counting switch CS, is already in the normal position shown in the drawings when the above-described clearing-out operation takes place, but the restoring circuit is provided through the contacts of relay 403 so that it will be effective when the calling subscriber replaces his receiver before the director has finished its operation.

i It will be noted that the above-mentioned restoring circuits all include the release-supervisory relay 401. Accordingly, relay 401 operates in the restoring circuits as soon as relay 403 falls back, and it remains operated until the last restoring circuit has been opened. At its upper armature, relay 401 reapplies ground potential to conductor 162 so as to maintain the director .guarded against, seizure until the clearing-out operation has been completed. At its inner-lower' armature, relay 401 closes a circuit to any suitable slow-acting alarm device so as to give an alarm signal in case one of the mechanisms fails to return to its normal position and open its restoring circuit, in which case the director is maintained guarded by way of conductor 162 until an attendant has located and disposed of the abnormal condition.

The apparatus in the director is now in the normal position shown in the drawings, and the director is in readiness to be used in setting up subsequent connections.

of the thousands selector THS is connected in circuitover the lower talking conductor in series with operating magnet 311 of the sequence switch SE of the connector C, but is not energized because of the current-limiting effect of the high-resistance element 318. At the same time, current is being supplied over both conductors incoming to the -thousands selector THS from the battery-feed relay 117 in the primary unit PU, maintaining the holding relay 20'1 energized in the thousands selector THS, but the batteryfeed relay 117 is unable to operate at this time because of the current-limiting eti'ect of the high-resistance element 207.

When the subscriber at substation B responds to the..ringing of his bell by removing his receiver, he closes a direct-currentbridge across the conductors of' his line, thereby permitting the ring-cut-ofi' relay 303 in the connector C to operate. Upon operating, relay 303 closes a locking circuit for its upper winding at its inner-upper armature through contacts of the operated release relay 301 and contacts of the non-operated relay 302; it opens an additional point in the circuit of release magnet 308 at its lower armature; and at its upper and lower armatures it opens the ringing circuit and completes the talking connection between wipers 315 and 317 and the incoming conductors 285 and 287, respectively, at the same Vtime disconnecting conductors 285 and 287 from their locall connections in the connector C.

ln the thousands selector THS, the battery-feed relay 203 now en-ergizes over the called line, as it is now supplying transmitter current to the called line through the selector HS and the connector C. Upon energizing, relay 203 places a shunt around the high-resistam-.e element 207, thereby incre-asing the current flow over conductors 185 and l87 sutiiciently to permit battery-feed relay 117 oi the primary unit to operate. Upon operating, battery-feed relay 117 closes a circuit from the grounded con-ductor 147 and through the upper armature of the unoperated relay 115 and armature 140 for the answering supervisory relay 110. Relay 110 operates and closes a locking circuit for itself at its inner-upper armature to the grounded conductor 147 completes thel talking circuit between the calling and called lines' by Way otl eondensers 1,18 and 119 at its upperl armature and armature 137, at the same time disconnectingr the source of ringing tone. at the resting contacts of armature 137; and at armatures 131 an-d 136 reverses the connection between the incoming cond uctors 10G and 108 and the windings of line of relay 111. thereby reversing the direction of current Hou' over the calling line. This reversal of the direct-ion of current flow over the calling line is of no particular utility in the present case, but is used in order to control the coin-collect mechanism when a line equipped with a coin box is calling.

ln order to control the. momentary application ot' increased current from` the socalled booster battery 122 to bring about au operation of the margiimlly-adjusted meter M individual to the line of substation A, the answering supervisory relay 110 opens-the locking circuit of the slow-acting relay 114: at armature 133, and at armature 132 disconnects the. incoming release-trunk conductor 107 from ground through the inner-upper contacts of switch-through relay 109 and the upper contact-s of release relay 112 and connects it instead through the upper armature of the still-operated rel-ay 114 and resistance, 121 to the positive pole of battery 122. Battery 122 has a potential more positiv-e than ground potential, increasing the current flow through the marginally-adjusted meter M, as the battery 122 is now inj series' with the exchange battery. The primary unit PU is maintained guarded against seizure by any other lineswitch by the positive guarding potential supplied by battery 122, and the lineswitch LS is at the same time maintained operated in the usual manner. The meter M responds to the increased current flow and registers the completed connection.

After a slight interval, relay 114 falls back and reconnects the incoming conductor 107 to ground potential at the upper contacts of relay 112, disconnecting the booster battery 122. The restoration of relay 114 does .not cause the test circuit of the director selector DS through operated magnet 151 to be again completed, as this circuit is maintained open at armature 135 of the answering supervisory relay 110.

The two subscribers may now converse with each other as desired, the talking circuit being outlined by the heavy conductors. Current for the transmitter at the calling substation A is supplied through the Windings of line relay 111 of the primary unit PU, and current for the transmitter at the called substation is supplied through the windings of the battery-feed relay 203 of the incoming thousands selector repeater THS in the called oiiice.

Hecasing the estabh'shed connection TIL/1. c/Ued subscribe/r zfmgs up first It will now be assumed that the subscriber at the called substation B is the first to replace his receiver, whereupon battery-feed relay 203 in the thousands selector THS falls back and re-inserts the high-resistance 

